this post was submitted on 06 Dec 2023
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64
Fedora 40 Eyes The Ability To Boot Unified Kernel Images Directly (www.phoronix.com)
submitted 1 year ago by [email protected] to c/[email protected]
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[–] Dr_Willis 17 points 1 year ago* (last edited 1 year ago)

I am reminded of the ability MANY years ago to write the kernel file directly to a floppy disk, or start of a hard drive and somehow being able to boot that way.

I just can't recall how I did it, or WHY I did it.

Back when the kernel would fit on a floppy disk. I am truly showing my age.

6 yr old grandson found a box of old floppy disks and was asking what they were. He started stacking them up making card houses and roads for his matchbox cars. Glad he got some use out of those recycled AOL floppies.

[–] [email protected] 8 points 1 year ago (2 children)

Is this good?

[–] [email protected] 26 points 1 year ago* (last edited 1 year ago) (2 children)

It basically means instead of relying on a bootloader (e.g. GRUB or systemd-boot) the computer boots the kernel directly. Generally there should be no change besides having to use the BIOS menu to manually select a kernel.

[–] [email protected] 3 points 1 year ago (1 children)

Thank you, you're awesome!

[–] [email protected] 9 points 1 year ago

No problem! :)

FWIW, a lot of the DIY distros (Arch and Gentoo being the ones on most minds) allow this already so it's nothing new. It's just Fedora implementing it that's new I guess. If you're curious, the term to search is "EFISTUB".

[–] [email protected] 1 points 1 year ago (1 children)

Is the benifit making secure boot work better?

[–] [email protected] 0 points 1 year ago (1 children)

Presume so, that's what the article claims:

This latest UKI work for Fedora will lead to better UEFI Secure Boot support, better supporting TPM measurements and confidential computing, and a more robust boot process.

[–] [email protected] 1 points 1 year ago* (last edited 1 year ago) (1 children)

That's nice, stuff like that does make dual booting harder unfortunately

[–] [email protected] 1 points 1 year ago

I'd imagine that if you want a bootloader, the option is there as well. I can't imagine Fedora just doing away with that unless the bootloaders themselves are unmaintained.

[–] [email protected] 2 points 1 year ago

I think for most people they won't care either way.

Some people do legitimately occasionally need to poke around in GRUB before loading the kernel. Setting up certain kernel parameters or looking for something on the filesystem or something like that. For those people, booting directly into the kernel means your ability to "poke around" is now limited by how nice your motherboard's firmware is. But even for those people, they should always at least have the option of setting up a 2-stage boot.

[–] [email protected] 6 points 1 year ago

This is the best summary I could come up with:

Fedora 40 is eyeing the next phase of its unified kernel (UKI) support within the distribution that will include the ability to support booting to unified kernel image files directly without having to go through a traditional bootloader like GRUB or SD-Boot.

The second phase of Fedora's unified kernel support is looking at a boot path from the EFI SHIM to UKI directly without any bootloader present.

The UEFI boot configuration will get an entry for each kernel installed, newly-installed kernels are configured to be booted once but will then be made permanent after a successful boot, and also enabling UKI support for 64-bit Arm (AArch64).

This latest UKI work for Fedora will lead to better UEFI Secure Boot support, better supporting TPM measurements and confidential computing, and a more robust boot process.

Those interested in the latest UKI efforts for Fedora 40 can see this Fedora mailing list thread with more details.

The original article contains 153 words, the summary contains 153 words. Saved 0%. I'm a bot and I'm open source!

[–] [email protected] 3 points 1 year ago (1 children)

Is there not issues with filling up the NVRAM with efi entries, even if you're deleting old ones? I've bricked a computer by distrohopping so many times it couldn't write new entries.

[–] [email protected] 4 points 1 year ago (1 children)

I'm probably wrong, but NVRAM suggests that there should be some way to clear it. (Clearing the CMOS might if you can't do it in software)

[–] [email protected] 6 points 1 year ago

I've cleared entries before with efibootmgr.